If one roots of k(x−1)2=8x−14,k>0, is twice the other then the value of k is
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a
−2
b
64
c
2 or 64
d
2
answer is D.
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Detailed Solution
Given equation is k(x−1)2=8x−14, k>0 It can be written as k(x2−2x+1)=8x−14 ⇒kx2−(2k+8)x+k+14=0 Let the roots be α and 2α, then sum of the roots : α+2α= 2k+8k And product of the roots : α(2α) = k+14k ⇒ α= 2k+83k and 2α2= k+14k ⇒ 2(2k+83k)2= k+14k (∵ α= 2k+83k ) ⇒2(4k2+64+32k9k2)=k+14k ⇒ 8k2+64k+128 = 9k2+126k ⇒ k2+62k−128=0 ⇒ (k+64)(k−2) =0 ⇒ k=−64, 2. ∴ k=2 (∵k>0)